U.S. Pat. No. 7,436,988 describes a face authentication and recognition method that uses 2 dimensional images to form a 3 dimensional model, and verification of the identity of a person by comparison of the 3 dimensional model with reference data. A face profile line is extracted from the intersection of the symmetry plane of the face with the 3D model and properties of this line are used for verification of the identity of a person. The symmetry plane is found by forming a mirrored version of the 3D model and positioning the original 3D model and the mirrored version relative to each other in a way results in a best match. The procedure for finding the symmetry plane implicitly determines information relating to the location of the face, on the assumption that the face is the only substantially symmetric object in the modeled space. However, U.S. Pat. No. 7,436,988 does not discuss the problem of location determination.
Face recognition and face location determination are different tasks that involve different considerations. Face recognition is inherently person specific: the essence of face recognition is that different persons should be distinguished. Face location determination, on the other hand, is preferably person independent: the location should be determined independent of the unique personal features of the face.